UNIX Filesystems: Evolution, Design, and Implementation

The Early Days of UNIX

The research arm of the Bell Telephone Company, Bell Labs, had seen the need for a new computer operating system in the late 1950s. This resulted in the BESYS operating system which, although used internally, had limited distribution outside of Bell Labs. By the mid 1960s, third-generation computer equipment was emerging and the people at Bell Labs had to decide whether to create a new operating system or to adopt a third party OS. The decision was eventually made to join General Electric and MIT to create a new timesharing system called the MULTIplexed Information and Computing Service (MULTICS). This collaborative venture aimed to show that general purpose, multiuser operating systems were a viable solution. Based on a research operating system from MIT called the Compatible Time Sharing System (CTSS), the MULTICS project resulted in a wide range of new approaches. Amongst those working on MULTICS were Bell Lab researchers Ken Thomson and Dennis Ritchie, who would take many of the ideas from MULTICS and evolve them into what would become UNIX. As an example, many of the UNIX commands were based on commands of the same name in MULTICS, namely ls, cd, and pwd. Due to the high cost of development and the amount of time that it was believed MULTICS would take to complete, AT&T withdrew from the MULTICS project in 1969.

On an internal GE-645 computer at Bell Labs, the GECOS operating system was installed, which proved inadequate to many of the researchers. For ...